Amazon Nightmare

Hi there I am hoping someone can shed some light. I am not VAT registered but sell small on Amazon they have charged me VAT through Luxemburg. I have tried to get this refunded as have many, however, they tell me I need HMRC to send me a letter to prove I am a sole trader. Now here lies the issue HMRC say they don't send these either in PDF form in email or via post. Do you know what I can do? They have withheld my payments too

Hi Avongirl78 Hulme,
If you are not VAT registered then unfortunately there is nothing we can send out to you.
I am assuming that Amazon want to see evidence that you are in business so that they do not charge you the VAT.
If the marketplace do want evidence of you being in business I would recommending contacting them to see what else you could provide to them for their satisfaction.
Thank you.